Active tectonics of the Caribbean-North American plate boundary in Guatemala

• Applicant: Dr. Christoph Grützner
• Subject Area: Geology ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Geophysics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529303576

In this proposal we plan to study the two active fault systems that make up the Caribbean-North American plate boundary in Guatemala. The two fault systems are the left-lateral Polochic and Motagua faults. Geodetic data indicate that the Motagua Fault today is slipping much faster than the Polochic Fault, but geological observations suggest that the Polochic Fault was the faster one in the Miocene. Both faults caused strong (M>7) earthquakes during the historical and instrumental period. Essential aspects of how the plate boundary works are unknown, such as the recurrence time for large earthquakes, the possible interaction of the two parallel fault systems, and why the switch in fault activity happened. We primarily aim at reconstructing the faults’ Late Quaternary earthquake history with paleoseismological methods. This work will allow us to understand the recurrence interval of large earthquakes and to investigate if activity on one of the faults has an influence on the other structure. Since the active faults are not reliably mapped everywhere, we propose to use digital elevation models and hyperspectral satellite data to identify fault strands. We will use hyperspectral data from the Italian PRISMA mission and from the new German EnMAP satellite, which started its routine operation phase in November 2022. This innovative approach has – to our knowledge – not been applied so far and initial tests have confirmed that the fault trace can be identified at least in some places. Paleoseismological trenches will be opened at sites that we already identified and for which the logistics have been worked out. More trench sites will be chosen based on the outcome of the remote sensing investigations and field work. Additionally, we will run a paleostress analysis. This work will show if external forcing (like changes in the kinematics of the plate boundary) is responsible for the switch in relative fault velocity, or if parameters like the frictional properties of the faults caused the Polochic Fault to slow down and the Motagua Fault to speed up. We identified dozens of hard rock fault outcrops from which we can collect the data for the paleostress analysis. Our project is important for understanding how strain is distributed across faults systems and why. This has implications for fault physics in general, and for the regional seismic hazard in a vulnerable region. Public outreach thus plays an important role in the later stages of the project. Importantly, our proposal profits from an already established network of researchers and from the support of Guatemalan and American scientists.

• DFG Programme: Research Grants
• International Connection: Guatemala, USA
• Co-Investigators: Dr. Moritz Kirsch; Professorin Dr. Sumiko Tsukamoto
• Cooperation Partners: Professor Omar Gilberto Flores Beltetón; Professor Francisco Gomez; Professorin Tina Niemi; Professor Dr. Jonathan Obrist-Farner